OTTAWA - The Canadian Food Inspection Agency (CFIA) is warning there could be an expansion of a nationwide recall on frozen beef burgers contaminated with E. coli bacteria.

Barbara Jordan, the associate vice-president of operations for the CFIA, says investigators are now trying to determine whether the source of the bacteria is the beef or other ingredients in the Butcher's Choice Beef Burgers.

"The team is now focused on tracing the origin of the ingredients including spices and beef from the products that tested positive," said Jordan in a conference call Saturday from Ottawa.

"If the food inspection agency trace back... a contaminated ingredient, other facilities and products my be implicated and this could lead to further recalls."

The affected product under the current recall are Butcher's Choice Hickory Barbecue Beef Burgers and Butcher's Choice Garlic Peppercorn Beef Burgers which are sold in 1.13 kilogram packages (UPC codes 0 60383 89364 4 and 0 60383 89363 7) at Loblaw grocery stores across the country.

Consumers are being told not to eat any of these burgers with any expiry date.

No illnesses have been directly linked to the recall.

Officials were first made aware of the possible contamination on Dec. 5 when the Public Health Agency of Canada notified the agency about five people who had become sick after eating burgers with the bacteria in Ontario and Quebec.

But Jordan says officials have not yet been able to determine if the illnesses are connected to these particular burgers.

The recalled burgers were produced at Cardinal Meat Specialists in Brampton, Ont., and that an investigation had found that the plant was following proper food safety protocols.

The CFIA says it is testing additional products collected from across the country.

Food contaminated with E. coli can cause serious and even life-threatening illnesses.